37. PRELIMINARY ORGANIC GEOCHEMISTRY OF LAMINATED VERSUS NONLAMINATEDSEDIMENTS FROM HOLES 479 AND 480, DEEP SEA DRILLING PROJECT LEG 641

Bernd R. T. Simoneit,2 Institute of Geophysics and Planetary Physics, University of California-Los Angeles,Los Angeles, California

ABSTRACT

Laminated and nonlaminated sediments from Holes 480 and 479 have been analyzed for potential differences in thecomposition of organic matter. Their lipid composition is very similar and indicates a primary autochthonous microbialorigin and some influx of allochthonous higher-plant detritus. The nonlaminated sections contain relatively more ter-rigenous plant wax detritus versus autochthonous residues and a much greater amount of perylene than the laminatedsections.

INTRODUCTION

Holes 479 and 480 were cored 6 km apart on theGuaymas Slope (for location, see Simoneifs introduc-tion to shore-based studies, this volume, Pt. 2). The sed-iments consisted primarily of laminated and nonlami-nated, muddy diatomaceous ooze with some rare inter-bedded sands and thin diagenetic-dolomite layers (Cur-ray et al., 1979). These laminated sediments are prob-ably varves, resulting from the interaction of two sea-sonal events: the summer rains that introduce terrige-nous clays to the region and diatom blooms caused byupwelling from northwest winter winds (Curray et al.,1979; Schrader et al., 1980). The preservation of lami-nated sediment sections indicates oxygen depletion inthe bottom waters.

Samples for this study were chosen from Hole 480 toexamine any potential differences in the composition ofthe organic matter in laminated versus nonlaminatedsections. A sample of driftwood and a laminated sedi-ment sample, both from Hole 479, were also analyzedfor comparison.

METHODS

The samples from Hole 480 were taken by scraping a fresh surfaceof split core. Each 10-cm interval represents a maximum of 100 y. ofsedimentation. The small samples (0.5-2 g) were freeze dried and thenextracted repeatedly with a mixture of chloroform and methanol (1:1)using ultrasonication. The extracts were concentrated on a rotaryevaporator and then subjected to column chromatography (micro-scale) on silica gel; hexane was the eluent. The total hydrocarbon frac-tions were collected, concentrated, and analyzed by gas chromatog-raphy (GC) and GC/mass spectrometry (GC/MS). After esterifica-tion, the extract from Sample 479-29-5, 114-116 cm was separated bythin-layer chromatography; hydrocarbons and fatty-acid esters werethen analyzed.

The GC analyses were carried out on a Hewlett-Packard 5840 gaschromatograph using a 25 m × 0.20 mm fused-silica capillary columncoated with SP-2100. The chromatograph was programmed from 35to 280°C at 4°C per mih.; He was the carrier gas.

Curray, J. R., Moore, D. G., et al., Init. Repts. DSDP, 64: Washington (U.S. Govt.Printing Office).

2 Present address: Oregon State University, School of Oceanography, Corvallis, Oregon97331.

The GC/MS analyses were carried out on a Finnigan 4000 quadru-pole mass spectrometer interfaced directly to a Finnigan 9610 gaschromatograph equipped with a 30 m × 0.25 mm fused-silica capillarycolumn coated with SE-54. The GC conditions for the GC/MSanalyses were the same as those for the analytical GC system. MS datawere acquired and processed with a Finnigan-Incos 2300 data system.

RESULTS AND DISCUSSION

The sample descriptions and analytical results aregiven in Table 1. The samples from Hole 480 were toosmall for the usual geochemical parameter analyses;thus, only the hydrocarbon data are reported here.

The total-lipid yields (Table 1) are high, and largerconcentrations occur in the laminated (varved) sectionsof Hole 480. The same is true for the total hydrocarbonyields. The ft-alkane distributions are quite similar; onlysubtle differences exist between the laminated (Fig. 1A,C) and nonlaminated (Fig. IB, D) samples. The «-al-kanes range from C12 to C33, and usually have threemaxima—at C15, C21 to C23, and C29—and a strong odd-to-even carbon number predominance >C23. The ho-mologs <C23 represent autochthonous marine lipids,where undegraded microbial residues < C19 and degradedalgal material in the region of C19 to C23 occur (Simon-eit, 1975, 1978a, in press). The homologs > C23 with theodd-carbon-number predominance represent an alloch-thonous component derived from terrestrial higher-plantwax (Simoneit, 1975, 1978a,b). The terrigenous alkanesoccur in about equal absolute amounts in both types ofsamples, but their relative proportions versus the micro-bial residues are greater in nonlaminated samples. Thisindicates that, during a depositional period that pro-duces the nonlaminated sequences, the terrigenous in-flux of mineral detritus is high, but the terrestrial or-ganic matter associated with the detritus is lower ofabout the same.

The isoprenoid hydrocarbons occur in significantamounts (Fig. 1), but the Pr/Ph ratios of the Hole 480samples are > 1 (Table 1). All samples contain elementalsulfur, and the amounts do not correlate with the lami-nated versus nonlaminated sections. These data are in-conclusive regarding partially euxinic conditions causedby the rapid sedimentation (Didyk et al., 1978). The

921

B. R. T. SIMONEIT

Table 1. Sample descriptions and analytical results for core material, Holes 479 and 480.

Sample a

(interval in cm)

480-2-3, 21-30

480-3-3, 107-119

480-19-1, 58-59

480-19-1, 130-150

479-9-2, 28

479-29-5, 114-116

Sub-bottomDepth

(m)

8.0

13.7

90.9

91.7

71.3

266.7

Lithology

laminateddiatom oozenonlaminateddiatom oozelaminateddiatom oozenonlaminateddiatom oozewood

laminateddiatom ooze

TotalLipids

(µg/g)b

1327

976

1316

748

800

490

TotalHC

(Mg/g)b

435

370

490

250

56

64

CPIC

1.3

1.5

1.4

1.7

2.21

1.6

n-alkanes

Maxima

15, 21, 29

15, 22, 29

15, 21, 27

15, 17, 22, 29

19, 22, 29

17, 29, 31

Pr/Ph

1.4

1.7

1.1

1.3

0.83

0.9

Perylene

O»g/g)b

0.24

1.2

0.41

3.2

n.d.

2.0

Kerogen

H/C, N/C e 5 1 3 C (‰) f

_ —

— —

_ _

0.70 -23.4(0.013)1.20 -19.9

(0.046)

Note: n.d. = not detected; dash = not determined.a All samples are late Quaternary.° Weights based on dry sediment.c Carbon preference index summed from C10-C35, odd/even.° The dominant homolog is in italic.^ Determined by Microanalytical Laboratory, Department of Chemistry, University of California—Berkeley; N/C in parentheses.' Reported versus PDB standard.

Pr/Ph > 1 could however be caused by the immaturityof the organic detritus, which could invert to < 1 on fur-ther maturation (e.g., Sample 479-29-5, 114-J16 cmfrom greater sub-bottom depth; Fig. IF).

Perylene (C20H12) occurs in higher concentrations inthe nonlaminated sequence (Table 1). This compoundhas been found in many euxinic sediments and appearsto be another indicator of oxygen depletion in deposi-tional environments (e.g., Simoneit, 1978a, 1978b; Si-moneit and Mazurek, in press; Louda and Baker, inpress). Whether it is a terrigenous marker or an autoch-thonous product is still a matter of debate and investiga-tion.

The molecular markers, such as steroid and triterpe-noid residues from autochthonous sources, are not de-tectable; however, diterpenoid residues from terrestrialresinous plants occur in minor amounts and at higherconcentrations and diversity in the nonlaminated sec-tions. The diterpenoid residues comprise retene, dehy-droabietic acid, dehydroabietane, and minor amountsof dehydroabietin and methylethylphenanthrene (Si-moneit, 1977). These compounds probably entered thissedimentary environment as resin microparticles.

The kerogens from Hole 480 are immature and ofprimarily marine origin (Peters and Simoneit, this vol-ume). The analysis also indicates a difference in kerogenconstitution for the laminated, euxinic (high hydrogenindex/low oxygen index) versus the nonlaminated, oxicsequences (i.e., low hydrogen index/high oxygen index;Peters and Simoneit, this volume, Pt. 2).

The wood sample (479-9-2) had significant lipid andhydrocarbon contents (Table 1). The /z-alkanes (Fig. IE)primarily consist of plant wax (> C24) and a lesser com-ponent of autochthonous material. Once sedimented,the autochthonous lipids were probably absorbed fromthe surroundings by the lignite, and the plant-wax resi-dues were brought in with the fragment. The H/C of thekerogen (extracted, demineralized residue) is 0.70, theN/C is 0.013, and the δ13C is -23.4% (Table 1). Ex-cept for H/C, these values do not indicate an originfrom peat or vascular plant detritus (C3 or Calvin cy-cle), where typical data are in the following ranges:H/C = 1.0, N/C = 0.03-0.06, and δ13C = -27--28%

(Stuermer et al., 1978). For C4 plants (Hatch-Slack cy-cle), the δ13C range from - 13 to - 23% (Galimov, 1980).This sample may represent a primary fragment of a C4

plant or a highly oxidized coal fragment (C3 plant),where the light carbon isotopes have been preferentiallyremoved, and/or the terrigenous organic matter was di-luted with autochthonous marine detritus during preser-vation and coalification.

Sample 479-29-5, 114-116 cm is about 267 meterssub-bottom, and is immature and unaltered. The lipidyield is high, and the /i-alkanes (Fig. IF) exhibit a bi-modal distribution, ranging from C1 0 to C35 with max-ima at C17 and C31. The homologs > C27 with the strongodd-to-even carbon number predominance are derivedfrom allochthonous plant wax. The homologs < C24 arefrom autochthonous microbial sources (Simoneit, 1975,1978a, in press). The Pr/Ph is less than one, and pery-lene and elemental sulfur are present, indicating par-tially euxinic paleoenvironmental conditions of sedi-mentation (Didyk et al., 1978). The distribution of n-fatty acids is bimodal, with maxima at C1 6 and C2 6 and astrong even-to-odd carbon-number predominance, typi-cal for biogenic sources (Fig. 1G). The homologs >C 2 1

are derived from terrigenous plant wax, and those < C2 0

are from autochthonous microbial sources (Simoneit,1975, 1978a).

The molecular markers confirm this sample's imma-turity and primarily consist of triterpenoid, steroid, andditerpenoid residues. The triterpenoids (Fig. 1H) com-prise the 17j3(H)-hopane series (C27, C29-C32), lesseramounts of 17α(H)-hopanes, hop-17(21)-ene, and iso-hop-13(18)-ene. These compounds are of an autochtho-nous marine origin and are geologically immature (Our-isson et al., 1979; Simoneit and Kaplan, 1980; Dastil-lung and Albrecht, 1976). The steroid residues in the hy-drocarbon fraction consist of ster-2-enes and ster-4-enes(in nearly equal proportions), diasterenes, and a minoramount of steranes. They range from C2 6 to C30; C2 7 isthe dominant homolog in all cases. The inferred sourceof these compounds is autochthonous microbial residuein the early stages of diagenesis (Huang and Meinschein,1979; Simoneit, 1978a; Simoneit and Philp, this vol-ume, Pt. 2). The diterpenoid residues occur primarily as

922

480-19-1, 1 30-1 50 cm

29

10

3.0π

10

31

10 ' I '20

' I '30

40 10

I 1 6 479-29-5

26

100-

H

a.

25

I

! II! i

479-29-5

17α(H)17ß(H)isomonoene

i i i30C

135

Figure 1. Distribution diagrams for various compound series, Holes 479 and 480. «-Alkanes [dotted line indicates isoprenoids]: A. Sample 480-2-3, 21-30 cm (laminated); B. Sample 480-3-3,107-119 cm (nonlaminated); C. Sample 480-19-1, 58-59 cm (laminated); D. Sample 480-19-1, 130-150 cm (nonlaminated); E. Sample 479-9-2, 28 cm (driftwood); F. Sample 479-29-5, 114-116cm. n-fatty acids [dashed line indicates dehydroabietic acid]: G. Sample 479-29-5, 114-116 cm. Triterpenoids: H. Sample 479-29-5, 114-116 cm.

B. R. T. SIMONEIT

dehydroabietic acid (Fig. 1G) and retene and dehydro-abietin at low concentrations, indicating a minor influxfrom terrigenous resinous plants (Simoneit, 1977).

The kerogen of this sample has been analyzed byCurie point pyrolysis (Simoneit and Philp, this volume),and the data indicate that it is of an unaltered marineorigin. The pyrolysis product pattern is similar to thatobserved in kerogens from the Cariaco Trench (van deMeent et al., 1980) and Walvis Bay (Namibia) (Simoneitand Philp, this volume).

CONCLUSIONS

The laminated and nonlaminated sections have simi-lar lipid compositions, but differ in their absolute con-centrations of compound groups. In the nonlaminatedsections, the terrigenous plant-wax residues are moreconcentrated than the autochthonous marine compo-nents. Perylene is also more concentrated (by a factor ofnearly five) in those sections. These data can be inter-preted as follows: (1) A greater influx occurred duringthe homogeneous sedimentation and consisted of terrig-enous mineral detritus lower in lipids; however, theoverall terrestrial lipid influx remained approximatelyconstant. (2) The nonlaminated sections could also be aresult of partially oxic conditions in the water column.The slightly more refractive waxes would thus remain ina zone with a slower overall sedimentation rate, whereaslaminated sections would be deposited in more anoxicwaters, which are the result of higher algal productivityand more rapid sedimentation.

This terrigenous influence is further substantiated bythe kerogen data and the organic composition of thedriftwood fragment.

ACKNOWLEDGMENTS

I thank Dana Blumfield and Dara Blumfield for technical assis-tance, E. Ruth for GC/MS data acquisition, and Monica A. Mazurekand Dr. Kerry Kelts for reviewing the manuscript. Contribution 2133of the Institute of Geophysics and Planetary Physics, UCLA.

REFERENCES

Curray, J. R., Moore, D. G., Aguayo, J. E., et al., 1979. Leg 64 seeksevidence on development of basin in the Gulf of California. Geo-times, 24(7): 18-20.

Dastillung, M., and Albrecht, P., 1976. Molecular test for oil pollu-tion in surface sediments. Mar. Poll. Bull., 7:13-15.

Didyk, B. M., Simoneit, B. R. T., Brassell, S. C , et al., 1978. Geo-chemical indicators of palaeoenvironmental conditions of sedi-mentation. Nature, 272:216-222.

Galimov, E. M., 1980. C13/C12 in kerogen. In Durand, B. (Ed.), Kero-gen, Insoluble Organic Matter from Sedimentary Rocks: Paris(Editions Technip), pp. 271-299.

Huang, W.-Y., and Meinschein, W. G., 1979. Sterols as ecological in-dicators. Geochim. Cosmochim. Acta, 43:739-745.

Louda, J. W., and Baker, E. W., in press. Geochemistry of tetrapyr-role, carotenoid and perylene pigments in sediments from the SanMiguel Gap (Site 467) and Baja California Borderlands (Site 471):DSDP/IPOD Leg 63. In Haq, B., Yeats, R. S., et al., Init. Repts.DSDP, 63: Washington (U.S. Govt. Printing Office).

Ourisson, G., Albrecht, P., and Rohmer, M., 1979. The hopanoids.Paleochemistry and biochemistry of a group of natural products.PureAppl. Chern., 51:709-729.

Schrader, H., Kelts, K., Curray, J., et al., 1980. Laminated diatoma-ceous sediments from the Guaymas Basin Slope (Central Gulf ofCalifornia): 250,000-year climate record. Science, 207:1207-1209.

Simoneit, B. R. T., 1975. Sources of organic matter in oceanic sedi-ments [Ph.D. dissert.]. University of Bristol, England.

, 1977. Diterpenoid compounds and other lipids in deep-sea sediments and their geochemical significance. Geochim. Cos-mochim. Acta, 41:463-476.

., 1978a. The organic chemistry of marine sediments. In Ri-ley, J. P., and Chester, R. (Eds.), Chemical Oceanography, 2nded. (Vol. 7): New York (Academic), 233-311.

, 1978b. Organic geochemistry of terrigenous muds and va-rious shales from the Black Sea, DSDP Leg 42B. In Ross, D.,Neprochnov, Y., et al., Init. Repts. DSDP, 42, Pt. 2: Washington(U.S. Govt. Printing Office), 749-753.

_, in press. The composition, sources, and transport of or-ganic matter to marine sediments—The organic geochemical ap-proach. In Thompson, J. A. J. (Ed.), Proceedings of the Sympo-sium on Marine Chemistry into the Eighties: Ottawa (National Re-search Board of Canada).

Simoneit, B. R. T., and Kaplan, I. R., 1980. Triterpenoids as molec-ular markers of paleoseepage in Recent sediments of the SouthernCalifornia Bight. Mar. Environ. Res., 3:113-128.

Simoneit, B. R. T., and Mazurek, M. A., in press. Organic geochem-istry of sediments from the Southern California Borderland, DSDP/IPOD Leg 63. In Haq, B., Yeats, R. S., et al., Init. Repts. DSDP,63: Washington (U.S. Govt. Printing Office).

Stuermer, D. H., Peters, K. E., and Kaplan, I. R., 1978. Source indi-cators of humic substances and protokerogen: Stable isotope ra-tios, elemental compositions and electron-spin resonance spectra.Geochim. Cosmochim. Acta, 42:989-997.

van de Meent, D., Brown, S. C , Philp, R. P., et al., 1980. Pyrolysishigh resolution gas chromatography and pyrolysis gas chromatog-raphy-mass spectrometry of kerogens and kerogen precursors.Geochim. Cosmochim. Acta, 44:999-1013.

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